1. Field of the Invention
The invention relates to a cooling member and a lighting or signaling device for a motor vehicle comprising such a member.
2. Description of the Related Art
Motor vehicle lighting or signaling devices are composed by and large of a housing that is closed by a transparent wall, through which one or a plurality of light beams emerge. This housing accommodates at least one optical module, largely comprising a light source, and an optical system capable of modifying at least one parameter of the light generated by the light source for the emission of the light beam by the optical module. The optical system comprises optical components such as a reflector, a lens, a diffusing element or a collimator, or any other member capable of modifying at least one of the parameters of the light generated by the light source.
Developments in technology tend to favor the use of light sources constituted by at least one LED (Light Emitting Diode), because of their low energy consumption and the quality of the lighting obtained. LEDs do not radiate in an omnidirectional manner, but in a more directional manner than other light sources. The compact dimensions of the LEDs and their directional light radiation permit the dimensions to be reduced and the structure of the optical module to be simplified, with the advantage of facilitating its integration in the interior of the housing. In the course of their operation, however, LEDs produce heat which is detrimental to their performance, since the greater the rise in the temperature of an LED, the greater is the reduction in its luminous flux. The heat that is released may even give rise to problems relating to the adequate supply of electrical power to the LEDs. It is therefore necessary to make provisions in order to permit cooling of the one or more LEDs which constitute the light source of the optical module, so as to prevent an increase in the temperature of the LEDs beyond an acceptable operating threshold.
For this purpose, it is customary to equip the optical module with a finned heat dissipater. The heat generated by the light source is evacuated in this way towards the internal volume of the housing and/or towards the exterior of the housing, on the basis of a thermal exchange utilizing the surface area of the fins that make up the dissipater. The optimization of the thermal exchange, between the finned dissipater heated by the LED and the air, may be achieved by the enlargement of the surface area via an increase in the size and/or the number of fins of the cooling member. However, this solution is implemented by increasing the size of a flat supporting base. This has the disadvantage of resulting in the enlargement of the surface dimensions of the optical module, which must be avoided in order to facilitate its implantation in the interior of the housing. In addition, such implantation is likely to be difficult in view of the restricted nature of the space available to accommodate the one or more optical modules, and/or in view of the constraints associated with the general arrangement of the lamp unit in respect of its immediate environment when it is mounted on the vehicle. It is consequently appropriate to organize the cooling of the one or more optical modules in such a way as not to obstruct their implantation in the interior of the housing.
It is also necessary to take account of the fact that the volume of the means used for the cooling of the LEDs that are contained in the optical modules is dependent on the quantity of heat that they generate at their operating power, this in turn being dependent on the luminous intensity that is necessary for the emission of light by the corresponding light beam. The volume of the lighting devices may sometimes be large, however, and it is important to restrict their dimensions.
Furthermore, it is important to identify solutions which permit the exchange surface to be increased without compromising their reliability, in particular mechanically, and which are cost-effective.